The proposed experiments will use animal models to investigate the physiological origins of sequence memory impairments that have been associated with the dysfunction of the posterior cingulate cortex in humans with Alzheimer's disease. One experiment will measure the behavioral effects of reversible inactivation in the posterior cingulate cortex across early and late stages of sequence learning. This will allow a test of the hypothesis that the posterior cingulate cortex contributes to the learning of new sequences. A second experiment will assess the effects of lesions of cholinergic neurons in the basal forebrain that project to the posterior cingulate cortex, thus testing the role of cholinergic modulation in posterior cingulate function, A third experiment will test the effects of neural inactivation in the dorsal striatum of the basal ganglia, thus testing the hypothesis that the subcortical targets of the cingulate cortex help to encode well-learned visuospatial sequences. Together, the experiments will investigate the basic role of the posterior cingulate cortex in the encoding of sequence memories. They will also allow a better understanding of the structural basis of memory dysfunctions associated with early Alzheimer's disease.